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Carboxylic Acids & Derivatives

Carboxylic Acids & Derivatives. Dr. Michael P. Gillespie. Introduction. Carboxylic acids contain a carboxyl group (-COOH). The name carboxyl is derived from terms carbonyl and hydroxyl, the two structural units that make up the carboxyl group. Carboxylic Acids: Structure & Properties.

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Carboxylic Acids & Derivatives

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  1. Carboxylic Acids & Derivatives Dr. Michael P. Gillespie

  2. Introduction • Carboxylic acids contain a carboxyl group (-COOH). • The name carboxyl is derived from terms carbonyl and hydroxyl, the two structural units that make up the carboxyl group. Dr. Michael P. Gillespie

  3. Carboxylic Acids: Structure & Properties • Carboxylix acids are characterized by the carboxyl group. • The carboxyl group consists of two very polar functional groups, the carbonyl group and the hydroxyl group. • Carboxylic acids are therefore very polar compounds. • They can hydrogen bond to one another and to water. Dr. Michael P. Gillespie

  4. Carboxylic Acids: Structure & Properties • Consequently, they are soluble in water and boil at higher temperatures. • As the carbon content increases, the solubility decreases because the carboxylic acids become more hydrocarbonlike. Dr. Michael P. Gillespie

  5. Carboxyl Group Dr. Michael P. Gillespie

  6. Some Important Carboxylic Acids • Methanoic (formic) acid causes the burning sensation of ant bites. • Ethanoic (acetic) acid provides the zip to vinegars. • Polymers of lactic acid are used as biodegradable sutures and biodegradable plastic bags (potato peels are a great source of this lactic acid). Dr. Michael P. Gillespie

  7. Some Important Carboxylic Acids • Butanoic (butyric) acid is the odor associated with rancid butter. • When these carboxylic acids react with alcohols they produce esters, which contribute to the fragrance and flavor of many fruits. • Octanoic (caprylic) acid contributes to hunger sensations. • Citric acid provides sharp taste to foods, is a food preservative, and an antioxidant. Dr. Michael P. Gillespie

  8. Some Important Carboxylic Acids • Lactic acid provides a tangy flavor. • Oxalic acid is found in spinach and rhubarb and contributes to the formation of kidney stones. • Benzoic acid is a preservative in soft drinks, pickles, jellies, etc. • Salicylic acid is a disinfectant. Dr. Michael P. Gillespie

  9. Some Important Carboxylic Acids • Acetylsalicylic acid is aspirin. Hippocrates identified a bitter extract from willow bark that reduced fevers and relieved pain. Dr. Michael P. Gillespie

  10. Biodegradable Plastic • Polymers of lactic acid make sheets of plastic. • Polylactic acid (PLA) is produced by the fermentation of sugars. • Bacteria in soil can readily break down PLA. • When french fries are produced, nearly half of the potato is wasted (approximately 10 billion pounds of potato waste each year). • This potato waste can be used to make PLA. Dr. Michael P. Gillespie

  11. Preparation of Carboxylic Acids • Carboxylic acids are prepared by the oxidation of aldehydes and primary alcohols. • The primary alcohol is oxidized into an aldehyde, which is further oxidized into a carboxylic acid. Dr. Michael P. Gillespie

  12. Acid-Base Reactions • When strong bases are added to a carboxylic acid neutralization occurs. • This produces a carboxylic acid salt and water. Dr. Michael P. Gillespie

  13. Esterification • Carboxylic acids react with alcohols to form esters and water. Dr. Michael P. Gillespie

  14. Esters: Structure & Properties • Esters are mildly polar and have pleasant aromas. • Their boiling points and melting points are comparable to those of aldehydes and ketones. Dr. Michael P. Gillespie

  15. Preparation of Esthers • Esters are formed from the reaction between a carboxylic acid and an alcohol. Dr. Michael P. Gillespie

  16. Hydrolysis of Esthers • An ester can undergo hydrolysis to revert back to the parent carboxylic acid and alcohol. • Saponification is the base catalyzed hydrolysis of an esther. Soaps are made by this process. Dr. Michael P. Gillespie

  17. Acid Chlorides • Acid chlorides are noxious chemicals formed in the reaction of a carboxylic acid and reagants such as PCl3 or SOCl2. Dr. Michael P. Gillespie

  18. Acid Anhydrides • Acid anhydrides are formed by the combination of an acid chloride and a carboxylate anion. • Acid anhydrides can react with an alcohol to produce an ester and a carboxylic acid. Dr. Michael P. Gillespie

  19. Chemistry of Flavor & Fragrance • Carboxylic acids are often foul smelling. • Butyric acid produces the smell of rancid butter. • When carboxylic acids are converted to esters they produce pleasant smells. Dr. Michael P. Gillespie

  20. Phosphoesters • An alcohol can react with phosphoric acid to produce a phosphate ester (phosphoester). • When two phosphate groups are joined, the resulting bond is a phosphoanhydride bond. • These two functional groups are important to the structure and function of adenosine triphosphate (ATP), the universal energy currency of all cells. Dr. Michael P. Gillespie

  21. Thioesters • Thioesters are produced by the reaction between a thiol and a carboxylic acid. • This reaction is catalyzed by cellular enzymes. • This reaction helps with fatty acid metabolism. • Coenzyme A is the most important thiol in these reactions. Dr. Michael P. Gillespie

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